This type of rock breaking tool utilises a firing chamber to discharge a cartridge into the barrel. The tool is used by inserting the barrel into a pre-drilled holding rock which is filled with water prior to firing. On discharging the tool into the hole, the expansion of gases from the firing causes water pressure in the form of a shock wave, which splits and cracks up the rock.
Rock breaking tools of this type known to the applicant have an extended barrel which is located in the length of the pre-drilled hole, with the tip of the barrel having a radially expandable seal. This seal expands by reason of lateral openings in the barrel directing discharge gases against the inner radial surface of the seal, and the expanding seal grips the surrounding rock to hold the tool within the hole sufficiently long for the discharge shock to break up the rocks. Without such a device for holding the tool within the hole, the tool is inclined to shoot out under blow back forces and the energy intended for breaking up the rock, is to a large extent lost.
The barrel of this type of tool has lateral discharge outlets along its length to allow lateral impulsive discharge forces to operate on the rock surrounding the hole. The tip, itself apart from the lateral discharge outlets for expanding the seal, is closed off.
The above rock breaking tool and method of using it also requires that a fairly long hole be drilled to accommodate the length of the barrel and the lateral discharge outlet. This hole must also be fairly accurately dimensioned and not be of too wide a diameter, since this can also serve to disperse and waste the energy shock. The hole must also be relatively water-tight and the longer the hole that is drilled, the greater is the chance of a leakage.